1. Field of the Invention
This invention relates to a cutting element and in particular a cutting element suitable for use on a drill bit for use in the formation of boreholes.
2. Description of the Related Art
One form of cutting element for use on a drill bit comprises a table of superhard material, for example polycrystalline diamond, which is bonded to a substrate of a less hard material, for example tungsten carbide. Cutting elements of this type are well known and are available in a range of shapes and sizes for use in a range of applications.
This type of cutting element is manufactured using a high temperature, high pressure process in which a tungsten carbide substrate element, diamond powder and a binder catalyst, for example in the form of cobalt, are exposed to high temperature, high pressure conditions, resulting in the formation of chemical bonds between the diamond crystals of the diamond powder to form a polycrystalline diamond layer which is also bonded to the substrate element.
The polycrystalline diamond layer defines a matrix of interstitial volumes containing the binder catalyst material. It has been found to be advantageous to remove the binder catalyst material from at least the interstitial volumes located adjacent a working surface of the cutting element, as described in, for example, WO 02/24603 and WO 02/24601, as such treatment results in the working surface being of improved abrasion and impact resistance.
In use, the exposed, untreated part of the diamond layer tends to wear more quickly than the treated part with the result that an unsupported, protruding lip forms, and this effect is particularly apparent where the treated layer, i.e. that from which the binder catalyst is removed, forms only a relatively small proportion of the overall depth of the diamond layer. In such arrangements, there is a risk of the unsupported lip fracturing. It is an object of the invention to provide a cutting element in which this disadvantage is of reduced effect.